Stator ring assembly



March 20, 1962 H. w. WELSH 3,026,087

STATOR RING ASSEMBLY F'iled Aug. 13, 1957 5 Sheets-Sheet 1 INVENTOR.

A TTORNE Y.

March 20, 1962 H. w. WELSH 3,026,087

STATOR RING ASSEMBLY Filed Aug. 13, 1957 3 Sheets-Sheet 2 ATTORNE).

March 20, 1962 H. w. WELSH 3,026,087

STATOR RING ASSEMBLY Filed Aug. 13, 1957 3 Sheets-Sheet 3 IN VEN TOR.

Z! a I ar digs ZZZ 2 4 2321 /Z A TZ'ORNEY- llnited States Patent 913,026,087 STATOR RING ASSEMBLY Harvey W. Welsh, Indianapolis, Ind.,assignor to General Motors Corporation, Detroit, Mich, a corporation ofDelaware Filed Aug. 13, 1957, Ser. No. 677,933 Claims. (Cl. 253-78) Myinvention relates to stator vane ring assemblies for axial-flowturbomachines and, more generally, to such axial-flow machines. It isparticularly adapted to the requirements of axial-flow compressors suchas are employed in aircraft gas turbines, but is not limited thereto.

By way of explanation and background, it is well known that mostaxial-flow compressors and turbines have alternating annular rows offixed and moving blades. A ring of fixed blades may be referred to as astator ring. In most cases, the stator ring comprises an outer shroud,an inner shroud, and vanes extending radially between and fixed to theshrouds. The outer shroud is fixed to the compressor case and the innershroud ordinarily provides or supports a labyrinth seal acting againstthe rotor. In order to assemble the compressor, that is, to mount therotor in the stator structure, the compressor case ordinarily is splitalong a plane containing the axis of the compressor into two segments,or halves, which are fixed together at what is called the split line oneach side of the case. The stator vane rings likewise are made in 180degree sectors, or halves. The stator vane ring halves are fixed to thehalves of the compressor case. After the rotor has been mounted in onehalf of the case, the other half is placed over the rotor and the twohalves of the case are bolted together or otherwise joined at the splitlines.

- One purpose of the inner shroud is to increase the strength andstifiness of the stator vane structure. However, the usual practice ofdividing the inner shroud into two sections greatly reduces the strengthof the inner shroud and the restraint it places on the deflection of thevanes. It also increases local stresses in the shroud and vanes. Sincethe vane ring is deflected axially of the compressor by the load put onthe vanes by air flow, a rigid structure which minimizes this deflectionis highly desirable because it makes it possible to reduce stageclearances in the compressor and reduce distortion of the seal betweenthe inner shroud and the rotor.

My invention substantially eliminates the defects of the previous splitvane ring assemblies by providing a strong mechanical attachment betweenthe adjoining ends of the sections of the inner shroud so that the innershroud becomes a mechanical equivalent of a continuous ring. This iseffected by a coupling device which may be readily applied to fasten thetwo halves of the inner shroud together. Preferably, although notnecessarily, the attachment is such as to put the inner shroud rings intension. Thus, if a small clearance is provided between the shroudsections and the coupling pulls these together, the inner shroud and thevanes will be put in tension by the coupling and the outer shroud willreceive a com pressive load.

By this means, a vane assembly is provided which may be taken apart forassembly and disassembly of the compressor but which has mechanicalstrength substantially equivalent to a continuous 360 degree vaneassembly. The rigidity of the structure is high, and distortions withthe undesirable efiects referred to above are minimized.

A further advantage of a structure according to the invention and afurther feature of the invention is that the rigid fixing together ofthe halves of the vane ring assembly makes it unnecessary to provide arigid attachment between the outer shroud and the case.

ice

In the succeeding description of the preferred embodiments of theinvention, a structure is shown in which the case and vane rings are intwo sections. Three or more sections could be provided if desired, buttwo secticns are sufiicient to provide for assembly of the compressor.For conciseness, the term shroud or ring will be applied to the arcuatesections thereof as well as to the assembled 360 degree shroud or ring.

The nature of the invention and the advantages thereof will be moreclearly apparent from the succeeding detailed description of thepreferred embodiments of the invention and the accompanying drawingsthereof.

FIGURE 1 is a fragmentary sectional view of an axialfiow compressortaken on a plane containing the axis of the compressor.

FIGURE 2 is a partial transverse sectional view of the stator taken onthe plane indicated by the line 22 in FIGURE 1.

FIGURE 3 is a fragmentary view of a first form of shroud coupling takenon the plane indicated by the line 33 in FIGURE 2, with parts cut away.

FIGURE 4 is a sectional view taken on the plane indicated by the line 44in FIGURE 3.

FIGURE 5 is a sectional view taken on the plane indicated by the line5-5 in FIGURE 3.

FIGURE 6 is a view similar to the view of FIGURE 3 showing a second formof shroud coupling.

FIGURE 7 is a sectional view taken on the plane indicated by the line 77in FIGURE 6.

FIGURE 8 is a sectional view taken on the plane indicated by the line 88in FIGURE 6.

FIGURE 9 is a view similar to that of FIGURE 3 showing a third form ofshroud coupling.

FIGURE 10 is a sectional View taken on the plane indicated by the line10-40 in FIGURE 9.

FIGURE 11 is a view similar to that of FIGURE 3 of a fourth form ofshroud coupling.

' FIGURE 12 is a sectional view taken on the plane indicated by the line1212 in FIGURE 11.

FIGURE 13 is a sectional view taken on the plane in dicated by the line13-13 in FIGURE ll.

Referring first to FIGURES 1 and 2, which illustrate the generalarrangement of the compressor stator, the invention is illustrated asembodied in a compressor having a case fabricated from light metalsections. The case 15 includes a cylindrical outer shell 16 welded to abolting flange 17 at one end and having a suitable flange or the like(not shown) at the other end. The cylindrical casing 16 is defined bytwo semi-cylindrical segments or sections 13 having longitudinal boltingflanges 19 which may be fixed together by bolts 21 or any other suitableattachment. The bolting flange 17 is fixed by bolts 22 to a furthercasing section 23 of the engine. Generally L-shaped rings or stiffeners24 are welded or brazed to the inner surface of the case sections 18 toreinforce the case and locate the stator ring assemblies. Rings 26,extending axially from the inner edges of rings 24 and bands 27 brazedto the inner surface of the rings act to provide a labyrinth sealagainst the rotor blade shrouds. The successive stages of rotor blades28 are mounted on a rotor structure (not shown) and extend in proximityto the case. The rotor blades are provided with shrouds 29 which includecircumferential flanges 3i) cooperating with the seal bands 27.

Each stator vane ring comprises an outer shroud 32 made up of a flatring 33 and a hat-section ring 34 welded or brazed together. The statorvanes 36 are fixed to the outer shroud and include tangs 37 extendingthrough the web of ring 34. The flanges 38 at each edge of the outershroud bear against the seal rings 26 and the'side walls of thehat-section ring 34 bear against circumferen- 3 tial ribs 39 on therings 24 which locate the vane axially of the compressor.

To restrain the vane ring assemblies against rotation about the axis ofthe compressor, small keys or blocks 41 are brazed to the radialsurfaces of the hat-section rings 34. These blocks engage in notches 42cut in the ribs 39 of the rings 24. Two such locating means are providedsubstantially half-way between the split lines, one on each half of theouter shroud.

The inner ends of vanes 28 are rigidly fixedto the inner shroud ring 43,which is in two semi-circular sections. Suitable coupling means,indicated generally at 45 in FIGURE 2, are provided between the twosections of the inner shroud. The preferred structuresof these couplingmeans and typical inner shroud structures are shown in FIGURES 3 to. 13.

Referring now to FIGURES 3 to 5, the inner shroud 43 comprises an outerfrusto conical band 46 and an inner hat-section ring 47, these beingspotwelded together at their abutting margins. The vanes 28 are suitablyattached as, for example, by brazing to the inner shroud 43. Thecoupling 45 between the sections of the inner shroud is provided bystructure including cross mem ring here 48 spotwelded to the inside ofthe radial walls of the ring 47. A single tongue 49 which, as will beseen most clearly in FIGURE 5, is a sheet metal member folded into anI-section, is spotwelded to one of the cross members 48. Two tongues 51of similar structure to tongue 49 are spotwelded to the other crossmember 48 and extend so as to lie on either side of the tongue 49. Thesetongues define inclined wedging or ramp surfaces 52 which face towardthe shroud section on which the tongue is mounted and which face eachother when the intermediate tongue 49 is inserted between theoutertongues 51 in the assembly of the vane ring. As will be noted, the rampsurfaces are skewed to the axis of the compressor so that the couplingfits readily between the vanes '28. This skewing need be provided onlywhere the limited space between the vanes makes it desirable.

The two halves of the inner shroud are fixed together by two wedgingmembers 53 and 54 which are of sheet metal formed into a trapezoidalcross section to provide wedging surfaces 56 to cooperate with the rampsurfaces 52'of the tongues. The wedge members 53 and 54 are pulledtogether by a socket head screw 57, the head of which bears against theinner web of the wedge 53 and which cooperates with a self-locking nut58 spotwelded to the inner web of wedge 54. As will be apparent, upontightening the bolt into the nut, the Wedges are pulled together andforce the ramp surfaces. 52 apart, pulling the shrouds together. Whenthe stator ring is fully assembled, the ends of the shroud sections,which are shown spaced by a gap 59, are pulled into abutting relation. Avery strong and rigid attachment between the stator rings is thusprovided and the inner shroud is put in tension.

, As will be apparent, both of the couplings 45 at the two 'SPllt linesmay be identical. The bolt 57 may be reached by a suitable tool totighten or release the coupling through the clearances between thestages or through a hole (not shown) in theouter shroud before the tophalf of the case is assembled onto the lower half. The bolt 57 extendsthrough a hole 61 in the tongue 49 which has suificient clearancecircumferentially of the shroud to allow movement of the tongue relativeto the bolt.

The second form of coupling, illustrated in FIGURES 6 to 8, employs thesame principle of wedging action to pull the shroud sections together asthat previously described, but isstructurally different. The innershroud may be substantially the same as that previously described, madeup of an outer band 46 and an inner hatsection ring 47. A projectingchannel section tongue 63 is welded to the bottom and side flanges ofone hata section 47 and a similar tongue 64 is similarly fixed to theother hat-section 47. Tongue 64 has a radial ofiset this tongue isnarrower than tongue 63 so that tongue 64'may enter into tongue 63with'the shroud sections in proper alignment. Tapered slots 68 and 69are machined in the side webs of tongues 63 and 64, respectively. Awedge or tapered block 71 is pulled radially into the slots 68 and 69 bysocket head bolt 72 which threads into a self-locking nut 73 spotweldedto the tongue 63. A paral lelogram-shaped plate 74 fixed to the wedge 71substantially closes the gap between the shroud bands 46. The bolt 72passes through suitable clearance openings 76 and 77 in the tongues 63and 64. When the shroud ends have been brought into proper relation withthe tongues overlapping, the wedge 71 may be placed in the slots 68 and69 and the bolt 72 is inserted and tightened. The wedge 71, acting onthe ramp. surfaces of the slots, pulls the parts of the stator ringtogether and puts them in tension. The wedge 71 is pulled in until itengages both sides of the slots' 68 and 69, firmly locking the sections.The figure shows the partsas they appear before the coupling has beentightened fully.

FIGURES 9 and 10 illustrate a third form of coupling similar in manyrespects to that of FIGURES 3 to 5. The overlapping tongue members arean inner tongue 78 fixed to one shroud and outer tongues 79 fixed to theother shroud. As in FIGURE-'3, these-tongues are generally of I-sectionand aregfixed to cross members 48. However, the tongues 78 and 79 aresmall machined metal blocks rather than folded sheet metal. They haveslots 80 which provide ramp surfaces 86 similar to those previouslydescribed-with respect to FIGURE 3, except that there are ramp surfacesat each side of the slot, and are pulled together by two wedges 81 and82 which are similar in exterior contour to those-previously described.but which are solid metal. A parallelogram-shaped metal sheet 83, fixedto the outer surface of wedge '81 and extending the full width of band46, substantially fills the gap between the ends of the adjoining'bands46. A socket head bolt 84 mounted in the wedge 81 threads into wedge 82,pulling the wedges against the ramp sur faces 86 of the tongues to drawthe shroud sections to gether. A self-locking nut is not employed inthis form. Instead, tabs 87 extending from-the sheet 83 may be bent downinto slots. 88. These tabs prevent the bolts from loosening because ofvibration of the structure. The bolt 84 is tightened until the wedgesengage both sides of slots 80, bearing against all the ramp surfaces, oruntil the ends of the shroud parts: 46 and 47 engage the wedges. Thestructuremay be proportioned for-either result.

The fourth embodiment of the invention, shown in FIG- URES 11 to 13, ismore closely related to the form of FIGURE 6 than to the otherspreviously described. In this form, the inner shroud 43 may be similarto those previously described, but the ends of the sections of theshroud are joined on a plane 91 containing the axis of the compressor.Two tongues 92 on one of the shrouds are defined by strap membersspotwelded to the radial walls of the hat-section 47. The tongues 92have tapered or V-shaped slots 93 cut into-them. A channel sectiontongue 94, the web of which lies adjacent the band 46, is spotwelded tothe other shroud section. The projecting end of tongue 94 is reduced inwidth so as. to fit closelyv between the tongues 92. Slots 96 are cutinthe tongue 94 which are of the same proportionsasthe slots 93. Acountersunk bushing 97 is welded to the inner surface of the shroud ring46 on which the tongues 92 are mounted. A slot 98 in the web of tongue94 provides clearance for this bushing. The wedge 99 which draws theshroud sections together is a rectangular block with chamfered ends,asindicated at 101-. A machine screwltlZ received in the bushing 97 andthreaded into the wedge 99 pulls the wedge radially outward, thechamfered surfaces engaging the ramp surfaces of the slots 93 and 96 topull the endsof the shrouds into firm abutment at the plane 91.

:It will be apparent that the several forms of the invention disclosedhave a common principle of action, although the structures arediversified. Depending upon the dimensions of the shroud and the vanering structure and other considerations, one or another might be mostsuitable in a particular installation. All provide a strong, rigidconnection between the sections of the shroud ring and all are easilyapplied and released.

In the assembly of the compressor incorporating the invention, the lowervane ring sections may be inserted into the lower half of the case. Therotor is then mounted on the lower half of the case and the upper halvesof the vane rings are fixed to the lower halves. The upper half of thecase is then mounted over the vane ring assemblies and rotor and boltedto the lower half.

While structure to bolt each outer shroud section of the vane ring tothe corresponding section of the case may be provided, as isconventional, such bolting may be accomplished after the case has beenassembled. However, since the invention provides essentially a rigid 360degree vane ring assembly, such bolting may be dispensed with. When thevane rings are lowered into the lower half of the case or the upper ofthe case is lowered onto the vane rings, the keys 41 are engaged in theslots 42 in the case, thus holding the vane rings against rotation.

The detailed description of the preferred embodiments of the inventionis not to be construed as restricting the invention, as manymodifications of structure may be made by exercise of skill in the artwithin the scope of the invention.

I claim:

1. An axial-flow turbomachine comprising, in combination, a caseincluding at least two segments joined along longitudinal split lines, astator vane ring mounted in the case comprising at least two arcuatesectors, each vane ring sector comprising an outer shroud, an innershroud, and vanes connected to the shrouds, and means for rigidlycoupling the adjacent ends of the inner shrouds including structures oneach inner shroud at the ends thereof and means attached to saidstructures locking said structures together.

2. An axial-flow turbomachine comprising, in combination, a caseincluding at least two segments joined along longitudinal split lines, astator vane ring mounted in the case comprising at least two arcuatesectors, each vane ring sector comprising an outer shroud, an innershroud, and vanes connected to the shrouds, and means for coupling theadjacent ends of the inner shrouds including structures on each innershroud at the ends thereof and removable connecting means engaging saidstructures and exerting a force circumferentially of the shrouds pullingthe segments mutually together.

3. An axial-flow turbomachine comprising, in combination, a caseincluding at least two segments joined along longitudinal split lines, astator vane ring mounted in the case comprising at least two arcuatesectors, each vane ring sector comprising an outer shroud, an innershroud, and vanes connected to the shrouds, and means for rigidlycoupling the adjacent ends of the inner shrouds including structuresfixed on each inner shroud at the ends thereof providing ramp surfacesthereon, a wedging mem ber movable transversely to the inner shroudsinto engagement with the ramp surfaces of both shrouds, and meansconnected to the wedging member and one of the shrouds for forcing thewedging member into engagement with the ramp surfaces.

4. An axial-flow turbomachine comprising, in combination, a caseincluding at least two segments joined along longitudinal split lines, astator vane ring mounted in the case comprising at least two arcuatesectors, each vane ring sector comprising an outer shroud, an innershroud, and vanes connected to the shrouds, and means for rigidlycoupling the adjacent ends of the inner shrouds including structuresfixed on each inner shroud at the ends thereof each having opposednotches therein providing ramp sur faces thereon, two opposed wedgingmembers movable radially into respective notches into engagement withthe ramp surface of both shrouds, and means connected to the wedgingmembers operable to draw the wedging members together.

5. An axial-flow turbomachine comprising, in combination, a caseincluding at least two segments joined along longitudinal split lines, astator vane ring mounted in the case comprising at least two arcuatesectors, each vane ring sector comprising an outer shroud, an innershroud, and vanes connected to the shrouds, means for rigidly detachablycoupling the adjacent ends of the inner shrouds, and radially slidableinterengaging means on the vane ring and the case restraining the vanering against rotation about its axis.

6. A vane ring structure for an axial-flow turbomachine comprising, incombination, at least two arcuate sectors, each sector comprising anouter shroud, an inner shroud, and vanes connected to the shrouds, anddetachable coupling means directly connected to the inner shrouds at theends thereof rigidly detachably coupling adjacent inner shroudstogether.

7. A vane ring structure for an axial-flow turbomachine comprising, incombination, at least two arcuate sectors, each sector comprising anouter shroud, an inner shroud, and vanes connected to the shrouds, andcoupling means on the inner shrouds at the ends thereof rigidly couplingadjacent inner shrouds together comprising parts fixed on each shroudand means dctachably connecting the said parts adapted to draw theshrouds together circumferentially.

8. A vane ring structure for an axial-flow turbomachine comprising, incombination, at least two arcuate sectors, each sector comprising anouter shroud, an inner shroud, and vanes connected to the shrouds, andcoupling means fixed on the inner shrouds at the ends thereof forrigidly coupling adjacent inner shrouds together comprising tonguesprojecting from one shroud, a tongue projecting from the other shroudadapted to extend between the firstmentioned tongues, the tongues havingspaced ramp surfaces thereon facing the shrouds from which they project,a member extending transversely of the shrouds engaging between andagainst the ramp surfaces, and means coupling the member to one of theshrouds adapted to force the member transversely of the shroud into thespace between the ramp surfaces to draw the shrouds together.

9. A vane ring structure for an axial-flow turbomachine comprising, incombination, at least two arcuate sectors, each sector comprising anouter shroud, an inner shroud, and vanes connected to the shrouds, andcoupling means fixed on the inner shrouds at the ends thereof forrigidly coupling adjacent inner shrouds together comprising tonguesprojecting from one shroud, a tongue projecting from the other shroudadapted to extend between the firstmentioned tongues, the tongues havingnotches in opposite faces thereof providing ramp surfaces thereon facingthe shrouds from which they project, two members extending transverselyof the shrouds seated in the respective notches between and against theramp surfaces, and means coupling the members together operable to drawthe said members toward each other into the notches.

10. A vane ring structure for an axial-flow turbomachine comprising, incombination, at least two arcuate sectors, each sector comprising anouter shroud, an inner shroud, and vanes connected to the shrouds, andcoupling means fixed on the inner shrouds, at the ends thereof forrigidly coupling adjacent inner shrouds together comprising tonguesprojecting from one shroud, a tongue projecting from the other shroudadapted to extend between the firstmentioned tongues, the tongues havingspaced ramp surfaces thereon facing the shrouds from which they project,a member extending transversely of the shrouds engaging between andagainst the ramp surfaces, and

7 means coupling the member to one of the shrouds adapted to force themember transversely of the shroud into the space between the rampsurfaces to draw the shrouds together, the member including a plateextending across and substantially filling said space between the inner5 shrouds.

Goeller June 25, 1940 8 Chester et al. Mar. 20, 1945 Summers May 25,1948 Howard Sept. 16, 1952 Clausen' Oct. 12, 1954 Boyd Nov. 9, 1954Russell et a1. Aug. 6, 1957 FOREIGN PATENTS Canada Ian. 8, 1957

